im a fan of the "only commons decks" and i like your idea, and while my whole "lets get this deck running with snapcasters liliana and some swords" side will have to be ignored, he is what i have to offer. Add some equipmet, somthing to give the skirge and the delver an extra boost for the quicker game. also Ponder, its cheap sets up delver and gives you a draw.

If you're only using commons, you have what might as well be the strongest Blue/Black creature in there, being the Delvers (Transformed) and the Drakes. the only thing stronger than those is Makeshift Mauler.